Sometimes when I am really feeling a difficult emotion like sadness or anger or fear (I intentionally don't use the phrase 'negative emotion) I just kind of hunker down and let myself feel the emotion, I use the emotion as an object of meditation. Instead of meditating on my breath or a mantra, I meditate on the emotion, and where it emerges in my body. I allow myself to really feel the emotion, to open to it nonjudgmentally and unconditionally (which is a form of unconditional love), and I adopt the meditative posture of 'witnessing' it as fully as I can as it is. I try to be as tenderly as possible 'with' the emotion fully from this place of nonjudgmental and unconditional witnessing.
I'm learning to do the same thing with those emotions I don't feel are difficult, I guess you could call them 'easy' emotions, like love and joy. I practice the same meditation of nonjudgmentally and unconditionally feeling it fully from a witnessing place and lovingingly opening to it.
The paradox is that when I do this practice with the easy emotions it opens the heart. And when I do this practice with the difficult emotions, it opens the heart. It might not be apparent in the same way as with the easy emotions, but it opens the heart.
I think and feel the heart just wants to be heard. Not fixed. Not forced to change. Not approached with any agenda. In its tears and in its joy, the heart simply wants to be heard. And held. And loved.
No paradox in that. No paradox in love.